UIPickerView(滚动选择控制器)

1.UIPickerView的宽度和高度是固定的,纵向是320*216,横向是568*162

2.属性:

    @property(nonatomic,readonly)NSIntegernumberOfComponents;      // 选择框的行数

    @property(nonatomic,assign)id<UIPickerViewDataSource> dataSource;     (类似于UITableView)     

    @property(nonatomic,assign)id<UIPickerViewDelegate>   delegate;              (类似于UITableView)  

     (BOOL)showsSelectionIndicator    // 是否显示选择指示器 ,即是一个蓝色的条

 pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
 //    指定Delegate
     pickerView.delegate=self;
 //    显示选中框
     pickerView.showsSelectionIndicator=YES;
     [self.view addSubview:pickerView];

以上可以在视图显示一个选取器，但是内容空白，pickerView.showsSelectionIndicator=YES;是这只当前选取器所选中的内容：

选取器上显示数据，必须依赖两个协议，UIPickerViewDelegate和UIPickerViewDataSource，把他们添加到ViewController.h文件中

 #import <UIKit/UIKit.h>

 @interface ViewController : UIViewController<UIPickerViewDelegate,UIPickerViewDataSource>
 {

     UIPickerView *pickerView;
     NSArray *pickerData;

 }

 @end

3.然后在.m文件的ViewDidLoad中初始化界面

 - (void)viewDidLoad
 {
     [super viewDidLoad];
     // Do any additional setup after loading the view, typically from a nib.

     pickerView = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, 320, 216)];
 //    指定Delegate
     pickerView.delegate=self;
 //    显示选中框
     pickerView.showsSelectionIndicator=YES;
     [self.view addSubview:pickerView];

     NSArray *dataArray = [[NSArray alloc]initWithObjects:@"许嵩",@"周杰伦",@"梁静茹",@"许飞",@"凤凰传奇",@"阿杜",@"方大同",@"林俊杰",@"胡夏",@"邱永传", nil];

     pickerData=dataArray;

 //     添加按钮
     CGRect frame = CGRectMake(120, 250, 80, 40);
     UIButton *selectButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
     selectButton.frame=frame;
     [selectButton setTitle:@"SELECT" forState:UIControlStateNormal];

     [selectButton addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];

     [self.view addSubview:selectButton];

 }

4.实现UIPickerView的代理方法，将数据显示在选取器上所需要几个方法

 #pragma mark -
 #pragma mark Picker Date Source Methods

 //返回显示的列数
 -(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
 {
     return 1;
 }
 //返回当前列显示的行数
 -(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
 {
     return [pickerData count];
 }

 #pragma mark Picker Delegate Methods

 //返回当前行的内容,此处是将数组中数值添加到滚动的那个显示栏上
 -(NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
 {
     return [pickerData objectAtIndex:row];
 }

前两个是数据源的代理方法，一个是返回列，有几个选取器就返回几，第二个是设置选取器有多少行，因为就这一个选取器，所以直接返回行数，即数组元素个数多少；第三个代理方法是将数组元素添加到了选取器上面显示 ；

说一下两个协议实例方法,参考http://www.cnblogs.com/edsioon/

   UIPickerViewDelegate中的实例方法

   // 当用户选择某个row时

  - (void) pickerView: (UIPickerView *)pickerView didSelectRow: (NSInteger)row inComponent:                               (NSInteger)component

// 当其在绘制row内容,需要row的高度时

- (CGFloat) pickerView:(UIPickerView *)pickerView rowHeightForComponent: (NSInteger) component

// 返回指定component.row显示的文本

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger) component

// 当picker view需要给指定的component.row指定view时,调用此函数.返回值为用作row内容的view

- (UIView *)pickerView: (UIPickerView *)pickerView view ForRow:(NSInteger) row forComponent:(NSInteger) component reusingView:(UIView *) view

// row的宽度

- (CGFloat)pickerView: (UIPickerView *)pickerView widthForComponent:(NSInteger) component

UIPickerViewDataSource中的实例方法

按照官方文档的说法,UIPickerViewDataSource这个协议仅有的功能就是提供picker view中component的个数和各个component中的row的个数,虽然名为datasource,但是它工作于MVC的C中

本协议仅有两个实例方法,均需要实现:

// 返回列数

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView

// 返回每一列对应的行数

- (NSInteger) pickerView:(UIPickerView *) pickerView numberOfRowsInComponent:(NSInteger) component

5.关于按钮响应事件，关于按钮的形成和添加响应事件不再提，前面都有，

 -(void) buttonPressed:(id)sender
 {
      NSInteger row =[pickerView selectedRowInComponent:0];
      NSString *selected = [pickerData objectAtIndex:row];
      NSString *message = [[NSString alloc] initWithFormat:@"你选择的是:%@",selected];

     UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示"
                                                     message:message
                                                    delegate:self
                                           cancelButtonTitle:@"OK"
                                           otherButtonTitles: nil];
     [alert show];

 }

@UIPickerView还有其他实例方法

// 获取指定列的行数

- (NSInteger) numberOfRowsInComponent:(NSInteger)component

// 刷新所有的列

- (void) reloadAllComponents

// 刷新指定的列

- (void) reloadComponent: (NSInteger) component

- (CGSize) rowSizeForComponent: (NSInteger) component

// 获取某列选择的行数

- (NSInteger) selectedRowInComponent: (NSInteger) component

// 选择一行

- (void) selectRow: (NSInteger)row inComponent: (NSInteger)component animated: (BOOL)animated

- (UIView *) viewForRow: (NSInteger)row forComponent: (NSInteger)component

附上源代码: http://download.csdn.net/detail/duxinfeng2010/4410909